The goal of this project is to produce clones of somatic cell hybrids which secrete monoclonal antibodies to human cell surface antigens. To explore this approach we will utilize human histocompatibility antigens (HLA) and melanoma associated antigens as model systems since they play a crucial role in immune defense and recognition of disease and and are useful as potential markers for immunodiagnosis of neoplastic disease, respectively. Splenocytes from rabbits or mice immunized to HLA or melanoma associated antigens will be fused with the murine myelona line P3-X63-Ag8. Fused cells will be selected, cloned and grown to mass cultures; supernatants from those cultures which contain antibody to HLA or melonoma associated antigens will be tested for allospecificity using serological and immunochemical techniques. The monoclonal nature of these antibodies will be shown by using various approaches including isoelectric focusing analysis and SDS-PAGE. Selected monoclonal antibodies will be used to develop highly sensitive radioimmunoassays to quantitate HLA and melanoma associated antigens on cells and in body fluids; these assays will facilitate the investigation of the clinical significance of these antigens. Monoclonal antibodies which exhibit allospecificity to HLA antigens will be used as models to assess whether such reagents are useful to elucidate some of the known and characteristic N-terminal amino acid sequences of these antigens. Monoclonal antibodies to melanoma associated antigens will be utilized to determine their molecular structure in order to elucidate their relationship to other components of the immune system. In addition the cell hybrid technology developed in this study should be useful in the preparation of monoclonal antibodies to other human cell surface markers.